Short-circuiting switch



July 17, .1928.

. 1,677,193 R. a. MGCURDY SHORT CIRCUITING SWITCH- Filed' sept. 2, 1927 Individual Il'wflrmer /y INVENTOR.

BY i W( A TTORNEY Patented July 17, 1928.

UNITED STATES PATENT OFFICE.

RALPH G. MG'CURDY, OF ENGLEWOOD, NEW JERSEY, ASSIGNOR T AMERICAN TELE- PHONE AND TELEGRAPH COMPAHY, A CORPORATION OF NEW YORK.

SHORT-CIRCUI TIN G SWITCH.

Application filed September 2, 1927. Serial No. 217,279.

This invention relates to series street lighttransformer through the holding coil 4 of ing circuits, and more particularly to the the alternating current relay. individual transformers which are associated With a lamp, such as 7, in service under one with each lamp lighted from the cirnormal conditions, harmonic voltages across at 6 uit, the secondary of the individual transformer If a lamp in a lighting system of the type are very small. Accordingly, under such indicated above fails (or burns out), the conditions, in the arrangement shown in the secondary of the individual transformer asdrawing, the relay contact 6 will remain sociated with that lamp is opened, and disopen. If, however, the lamp 7 fails, fairly ml 10 tortion is caused thereby in the alternating large harmonic voltages are set up across current waves in the system. This distorthe secondary of the transformer, and the tion may cause objectionable noise in teleodd'harmonic to which the combination 35 phone or other transmission circuits which is tuned will energize the operating coil 8 are exposed to induction from the lighting of the relay and cause the closing of con- 65 circuit. tact 6. This operation places a short-circuit The object of this invention is to prcacross the secondary winding 2 of the transvent such distortion and the interference former and prevents the harmonic voltage with transmission circuits consequent therefrom being impressed across the operating u on. V coil 3 of the relay. The cycle current WVith this object in view, i provide a (assuming that fundamental frequency) novel switching ar angenwnt for antomatiwill, however, flow through the holding coil cally short-circuiting the secondary winding 4: and serve to keep the contact 6 closed.

of an individual transformer when the 2.3- When the main series circuit of the lightsociated lamp fails, as will be more fully ing system is tie-energized, the relay contact 25 described below. will open, and if the defective lamp is re- The invention will be more clearly underplaced during the period of de-energization, stood when the following detailed descripthe relay circuit will be in condition for tion is read with reference to the accomsuitable operation when the lighting circuit panying drawing, which shows diagrammatis next energize 30 ically an individual transformer, a lamp What is claimed is:

connected therewith and my novel switch- In association with a transformer having ing arrangement. its primary Winding included in a series WVith reference to the details of the drawlighting circuit carrying alternating current ing the individual transformer has its priof a given frequency and a lamp having its 85 mary winding 1 in the main series circuit filament in series with the secondary windof the lighting system and its secondary mg of said transformer, an alternating curwinding 2 in series with the filament of the rent relay having an operating coil bridged incandescent lamp 7. An alternating curacross said secondary winding and a holdrent relay has an operating winding 3 and a ing coil, a condenser in series with said 40 holding winding 4. The operating coil 3 Operating coil in the bridge, said condenser is connected across the lamp circuit in series and said operating coil. being tuned to one with a condenser 5, as shown. The coinbinaodd harmonic of the lighting current fretion of the coil 3 and the condenser 5 is tuned quency, and a contact adapted to close when to one of the odd harmonics of the fundasaid operating coil isenergized and to place mental lighting current frequency; for ina short-circuit around. the secondary winding stance, if 60 cycle current is involved, the of the transformer through said holding combination may be tuned to the ninth harcoil. monic, or 540 cycles. When the relay opcr- In testimony whereof, I have signed my ates, the normally open contact 6 is closed. name to this specification this 31st day of 60 The closing of this contact places a short- August, 1927.

circuit across the secondary winding 2 of the RALPH G. MGCURDY. 

